Ash from the erupting Iceland volcano is forecast to affect some parts of Scotland between 6pm and midnight today, possibly affecting services from Barra, Benbecula and Tiree airports, air traffic control company Nats said.
One year after an Icelandic volcano brought much of Europe's air traffic to a halt, a cloud of ash from a new eruption could cause further disruption to airlines.
Iceland's Grimsvotn volcano, in its largest eruption for 100 years, began firing ash, smoke and steam 12 miles into the sky on Saturday.
The eruption has so far only affected Iceland, which, after initially playing down developments, closed its airspace. However, all airlines flying in European airspace were told yesterday to prepare for a possible spread of ash to the continent later in the week.
The ash cloud could spread to other parts of Britain, Spain and France later in the week, the Met Office said,
The eruption is much stronger than the one at the Eyjafjallajokull volcano last April which closed European airspace for six days, amid safety fears that the ash could damage jet engines.
Despite this, experts said the impact on air travel would be limited in comparison, due to favourable wind conditions and a heavier cloud of ash which is likely to fall to earth before it can spread so far.
"It could lead to some disruption, but only for a very limited time and only over a very limited area," claimed the University of Iceland's professor of geophysics, Magnus Tumi Gudmundsson.
"There is a very large area in southeast Iceland where there is almost total darkness and heavy fall of ash. But it is not spreading nearly as much. The winds are not as strong as they were [last year]."
The Icelandic air traffic control operator Isavia established a 120-nautical-mile no-fly-zone around the volcano, closed Keflavik Airport, the country's main hub, and cancelled all domestic flights. It said Keflavik would stay shut until at least noon on Monday.
Transatlantic planes – including Air Force One, which carried President Barack Obama to Ireland – were told to steer clear of Iceland.
With winds currently blowing the ash northwards, authorities said there was little risk of any further disruption to European or transatlantic airspace over the next 24 hours.
This could change, however, as low-pressure weather systems move into Europe and Scandinavia. There are concerns that northwesterly winds capable of dispersing ash towards the rest of Europe will pick up.
The ash from Grimsvotn – lying beneath the ice of the uninhabited Vatnajokull glacier in south-east Iceland, about 120 miles east of the capital, Reykjavik – turned the sky black yesterday and rained down on nearby areas, covering buildings, cars and fields in a thick layer of grey soot.
Civil protection workers helped farmers get animals to shelter and urged residents to wear masks and stay indoors.
Sparsely populated Iceland is one of the world's most volcanically active countries and eruptions are frequent.